Multicolor PVDs based on digital micro-mirror devices (DMDs) have become quite popular owing, in part, to their accurate color rendition, resolution, display size and overall cost. One important aspect of any video display system is its intensity—the ability to produce bright whites and vivid colors. In DMD-based projection systems, this means a bright light source and an efficient way to convey light from the light source to a screen.
Because the DMD itself is a relatively large part of the overall cost of a PVD, most of today's commercially available PVDs use a single DMD. Of those, most employ a white light source and filter the resulting white light through a color wheel that rotates among several colors. The single DMD renders each video frame color-by-color. However, the rendering rate is so high that the human eye perceives a full palette of colors for each frame.
The next generation DMD-based PVDs continue to employ a single DMD, but use as their light source multiple, separate, colored light sources, e.g., red, green and blue light sources. Often these colored light sources are lasers, noted for their intensity, efficiency, extremely low étendue, lifespan and color stability. While colored light sources offer significant advantages over a white light source and color wheel, it is apparent that the DMD has only a minor fraction of the dwell time of each frame (the reciprocal of the frame rate) to render a particular color. As a result, the majority of the light produced by each light source is lost or otherwise unusable, and the overall intensity of the system is less than perhaps it could be.
While the more recent DMD-based PVDs are well regarded, a simpler and lower cost optical system for conveying light through a DMD-based PVD would be beneficial. A method of generating so-called scan lines and a multicolor PVD employing such optical system or method would also be beneficial.